Re: [RFC v1 2/4] vfio-ccw: No need to call cp_free on an error in cp_init

Farhan Ali
2019-07-02T16:48:27Z

On 07/02/2019 12:15 PM, Eric Farman wrote:
>
>
> On 7/2/19 9:58 AM, Farhan Ali wrote:
>>
>>
>> On 07/02/2019 04:42 AM, Cornelia Huck wrote:
>>> On Mon,  1 Jul 2019 12:23:44 -0400
>>> Farhan Ali <alifm@linux.ibm.com> wrote:
>>>
>>>> We don't set cp->initialized to true so calling cp_free
>>>> will just return and not do anything.
>>>>
>>>> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
>>>> ---
>>>>   drivers/s390/cio/vfio_ccw_cp.c | 2 --
>>>>   1 file changed, 2 deletions(-)
>>>>
>>>> diff --git a/drivers/s390/cio/vfio_ccw_cp.c
>>>> b/drivers/s390/cio/vfio_ccw_cp.c
>>>> index 5ac4c1e..cab1be9 100644
>>>> --- a/drivers/s390/cio/vfio_ccw_cp.c
>>>> +++ b/drivers/s390/cio/vfio_ccw_cp.c
>>>> @@ -647,8 +647,6 @@ int cp_init(struct channel_program *cp, struct
>>>> device *mdev, union orb *orb)
>>>>         /* Build a ccwchain for the first CCW segment */
>>>>       ret = ccwchain_handle_ccw(orb->cmd.cpa, cp);
>>>> -    if (ret)
>>>> -        cp_free(cp);
>>>
>>> Makes sense; hopefully ccwchain_handle_ccw() cleans up correctly on
>>> error :) (I think it does)
>>>
>>
>> I have checked that it does as well, but wouldn't hurt if someone else
>> also glances over once again :)
>
> Oh noes. What happens once we start encountering TICs? If we do:
>
> ccwchain_handle_ccw() (OK)
> ccwchain_loop_tic() (OK)
> ccwchain_handle_ccw() (FAIL)
>
> The first _handle_ccw() will have added a ccwchain to the cp list, which
> doesn't appear to get cleaned up now. That used to be done in cp_init()
> until I squashed cp_free and cp_unpin_free. :(

Yup, you are right we are not freeing the chain correctly. Will fix it
in v2.
>
>>
>>> Maybe add a comment
>>>
>>> /* ccwchain_handle_ccw() already cleans up on error */
>>>
>>> so we don't stumble over this in the future?
>>
>> Sure.
>>
>>>
>>> (Also, does this want a Fixes: tag?)
>>
>> This might warrant a fixes tag as well.
>>>
>>>>         if (!ret)
>>>>           cp->initialized = true;
>>>
>>>
>